The present invention relates to a reactive liquid chromatography system, and a liquid supply device used in a system for analyzing a fluid sample, such as a reactive liquid chromatography system.
In a system for analyzing a fluid sample, such as a reactive liquid chromatography system, a check valve for preventing a reverse flow of the sample is positioned preceding or following a liquid supply pump for supplying the liquid sample (see, for example, Patent Document 1 (JP-A-2005-273514)).
FIG. 8 is a vertical cross-sectional diagram illustrating a configuration of a check valve and an example of a basic configuration of a typical check valve used in a high-pressure flow channel in a reactive liquid chromatography system or the like. The check value has a valving element that opens/closes a high-pressure flow channel inside a body of the valve depending on a slight pressure differential within the flow channel in order to prevent a reverse flow. For example, seals 83 and 84 are positioned on both ends of a check valve holder 82 housed in a stainless-steel check valve unit 81 to maintain air tightness of the body of the valve. A sapphire valve seat 83 and a ruby ball 84 are positioned inside the check valve holder 82. In the case of a flow from the left to the right in the Figure, the ruby ball 84 floats up from the sapphire valve seat 83 to open the valve. In the case of a flow from the right to the left, the ruby ball 84 is pressed against the sapphire valve seat 83 to close the valve. As described above, close contacting/floating of the ruby ball 84 with/from the sapphire valve seat 83 results in closing/opening of the check valve.
FIGS. 9 and 10 are vertical cross-sectional diagrams each illustrating a configuration of a check valve and a ferrule-equipped tap bolt used for connection with a pipe. A check valve unit 91, which is illustrated in FIG. 9, is incorporated in a flow channel by an upstream-side ferrule-equipped tap bolt 92 and a downstream-side connection unit 93. A pressure sensor 94 is positioned on the downstream side of the check valve. FIG. 9 illustrates the closed valve: where a pressure Pa inside an upstream-side pipe 95 is lower than a pressure Pb inside a downstream-side pipe 96. The ruby ball 84 illustrated in FIG. 8 is brought into close contact with the sapphire valve seat 83 by a pressure differential between both these pressures.
FIG. 10 illustrates the opened valve: the pressure Pa inside the upstream-side pipe 95 is higher than the pressure Pb inside the downstream pipe 96. The ruby ball 84 illustrated in FIG. 8 floats up from the sapphire valve seat 83 by a pressure differential between both these pressures to flow a fluid. A change in pressure at this time is ordinarily monitored by the pressure sensor 94 positioned at the downstream-side pipe 96. When a flow sensor is used instead of the pressure sensor 94, a change in flow rate that increases from zero, not a change in pressure, can be monitored. As described above, a check valve is used for making a fluid flow in a single direction.
However, by means of the conventional check valves, it cannot be determined whether or not a change in pressure or flow rate is caused by, for example, normal opening/closing operation of a check valve. For example, a change in pressure or flow rate may be caused by leakage from the seals 83 and 84 of the check valve holder 82 illustrated in FIG. 8, by leakage from a sealed portion of the ferrule-equipped tap bolt 92 illustrated in FIG. 9, and by clogging of the flow channel or the like. Furthermore, there may be a case where a normal opening/closing operation of a valve cannot be performed because of sticking of the valving element in the check valve or hunting of the valve due to fluctuation in pressure of a fluid.